1. Field of the Invention
The present invention relates to a printer head chip suitable for use in, for example, an inkjet printer, and a printer head using the printer head chip.
2. Description of the Related Art
A printer head of a type which discharges ink drops through a nozzle by generating pressure of ink bubbles inside an ink compressing chamber by heating a heat-generating resistor provided inside the ink compressing chamber is conventionally known. FIG. 11 is a sectional view of an example of a related printer head of this type.
In FIG. 11, a printer head chip 1 of the printer head includes a substrate 2, heat-generating resistors (heaters) 3 formed on the substrate 2, ink compressing chambers 4, and nozzles 5 formed at the top portions of the ink compressing chambers 4.
The heat-generating resistors 3 are used to compress ink that fills the inside of the ink compressing chambers 4 by the heat of the heat-generating resistors 3.
Each ink compressing chamber 4 is formed by a film 6 provided on the substrate 2 and a nozzle sheet 7 placed on the top portion of the film 6. The film 6 has a form which allows it to surround the vicinity of each heat-generating resistor 3 and forms a side wall of each ink compressing chamber 4. The nozzle sheet 7 forms the top wall of each ink compressing chamber 4. Further, the nozzles 5 having openings of predetermined diameters are formed in the nozzle sheet 7. Each nozzle 5 is disposed so as to be positioned above its corresponding heat-generating resistor 3.
An ink flow path 8 which connects to each ink compressing chamber 4 is formed in the printer head. In the example shown in FIG. 11, the ink flow path 8 is formed at both the left and right sides and the bottom side of the printer head chip 1. The ink flow path 8 is used to send ink into the ink compressing chambers 4, and is connected to ink supplying means (not shown).
In the printer head chip 1 having the above-described structure, ink is sent into the ink compressing chambers 4 through the ink flow path 8 from the ink supplying means. The ink sent into the ink compressing chambers 4 is heated by the heat-generating resistors 3. By pressure generated by this heating, the ink inside the ink compressing chambers 4 becomes ink bubbles. By expansion of the ink bubbles, ink drops i are discharged from the corresponding nozzles 5 and land onto a print medium such as paper.
However, in the above-described related technology, in order to supply ink to the ink compressing chambers 4 from the ink supplying means, it is necessary to form the ink flow path 8 over the length of the printer head chip 1 independently of the printer head chip 1, externally of the printer head chip 1. In other words, in order to supply ink into the ink compressing chambers 4, as shown in FIG. 11, it is necessary to provide the ink flow path 8 so that it is wider than the cross-sectional width of the printer head chip 1 and extends over the longitudinal direction of the printer head chip 1.
Therefore, this type of printer head has problems in that its overall size becomes large and in that its structure becomes complicated due to the formation of the ink flow path 8.
Here, as regards a relatively small printer head like that used in a serial printer, the size is not a very serious problem, but as regards, in particular, a long printer head like that used in a line printer, there is a problem in that the ink flow path 8 becomes large due to the long printer head.
In the above-described related technology, since the printer head chip 1 and the ink inside the ink flow path 8 are in contact with each other, a cooling effect of the printer head chip 1 by the ink can be expected. However, since the ink merely stays inside the ink flow path 8, there is a problem that a sufficient cooling effect cannot be provided.
On the other hand, when ink near the ink compressing chambers 4 contains bubbles, it is necessary to remove them. This is because, when the bubbles break when the ink is compressed, sufficient force is no longer exerted upon ink drops i in the direction in which they are discharged, so that the ink drops i tend to be improperly discharged.
When ink near the ink compressing chambers 4 contains bubbles, however, the bubbles can only be removed by suctioning them from the outside. Therefore, there is a problem in that ink is wastefully consumed.